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This patch introduces the file-system-session interface, provides an implementation of this interface in the form of an in-memory file system, and enables the libc to use the new file-system facility. The new interface resides in 'os/include/file_system_session/'. It uses synchronous RPC calls for functions referring to directory and meta-data handling. For transferring payload from/to files, the packet-stream interface is used. I envision that the asynchronous design of the packet-stream interface fits well will the block-session interface. Compared to Unix-like file-system APIs, Genode's file-system session interface is much simpler. In particular, it does not support per-file permissions. On Genode, we facilitate binding policy (such as write-permission) is sessions rather than individual file objects. As a reference implementation of the new interface, there is the new 'ram_fs' service at 'os/src/server/ram_fs'. It stores sparse files in memory. At the startup, 'ram_fs' is able to populate the file-system content with directories and ROM modules as specified in its configuration. To enable libc-using programs to access the new file-system interface, there is the new libc plugin at 'libports/src/lib/libc-fs'. Using this plugin, files stored on a native Genode file system can be accessed using the traditional POSIX file API. To see how the three parts described above fit together, the test case at 'libports/run/libc_fs' can be taken as reference. It reuses the original 'libc_ffat' test to exercise several file operations on a RAM file-system using the libc API. :Known limitations: The current state should be regarded as work in progress. In particular the error handling is not complete yet. Not all of the session functions return the proper exceptions in the event of an error. I plan to successively refine the interface while advancing the file-system implementations. Also the support for truncating files and symlink handling are not yet implemented. Furthermore, there is much room for optimization, in particular for the handling of directory entries. Currently, we communicate only one dir entry at a time, which is bad when traversing large trees. However, I decided to focus on functionality first and defer optimizations (such as batching dir entries) to a later stage. The current implementation does not handle file modification times at all, which may be a severe limitation for tools that depend on this information such as GNU make. Support for time will be added after we have revisited Genode's timer-session interface (issue #1). Fixes #54 Fixes #171
=================================
Genode Operating System Framework
=================================
This is the source tree of the reference implementation of the Genode OS
architecture. For a general overview about the architecture, please refer to
the project's official website:
:Official project website for the Genode OS Framework:
[http://genode.org/documentation/general-overview]
The current implementation can be compiled for 8 different kernels: Linux,
L4ka::Pistachio, L4/Fiasco, OKL4, NOVA, Fiasco.OC, Codezero, and a custom
kernel for the MicroBlaze architecture. Whereas the Linux version serves us as
development vehicle and enables us to rapidly develop the generic parts of the
system, the actual target platforms of the framework are microkernels. There
is no "perfect" microkernel - and neither should there be one. If a microkernel
pretended to be fit for all use cases, it wouldn't be "micro". Hence, all
microkernels differ in terms of their respective features, complexity, and
supported hardware architectures.
Genode allows the use of each of the kernels listed above with a rich set of
device drivers, protocol stacks, libraries, and applications in a uniform way.
For developers, the framework provides an easy way to target multiple different
kernels instead of tying the development to a particular kernel technology. For
kernel developers, Genode contributes advanced workloads, stress-testing their
kernel, and enabling a variety of application use cases that would not be
possible otherwise. For users and system integrators, it enables the choice of
the kernel that fits best with the requirements at hand for the particular
usage scenario.
Directory overview
##################
The Genode source tree is composed of the following subdirectories:
:'doc':
This directory contains general documentation. Please consider the following
document for a quick guide to get started with the framework:
! doc/getting_started.txt
If you are curious about the ready-to-use components that come with the
framework, please review the components overview:
! doc/components.txt
:'base':
This directory contains the source-code repository of the fundamental
frameworks and interfaces of Genode. Furthermore, it contains the generic
parts of core.
:'os':
This directory contains the non-base OS components such as the init process,
device drivers, and basic system services.
:'demo':
This directory contains the source-code repository of various services and
applications that we use for demonstration purposes. For example, a graphical
application launcher called Launchpad and the Scout tutorial browser.
:'base-<platform>':
These directories contain platform-specific source-code repositories
complementing the 'base' repository. The following platforms are supported:
:'linux':
Linux kernel (both x86_32 and x86_64)
:'pistachio':
L4ka::Pistachio kernel developed at University of Karlsruhe.
See [http://genode.org/community/wiki/GenodeOnL4kaPistachio]
:'fiasco':
L4/Fiasco kernel developed at University of Technology Dresden.
See [http://genode.org/community/wiki/GenodeOnL4Fiasco]
:'foc':
Fiasco.OC is a modernized version of the Fiasco microkernel with a
completely revised kernel interface fostering capability-based
security. It is not compatible with L4/Fiasco.
See [http://genode.org/community/wiki/GenodeOnFiascoOC]
:'okl4':
OKL4 kernel (x86_32 and ARM) developed at Open-Kernel-Labs.
See [http://genode.org/community/wiki/GenodeOnOKL4]
:'nova':
NOVA hypervisor developed at University of Technology Dresden
See [http://genode.org/community/wiki/GenodeOnNOVA]
:'codezero':
Codezero microkernel developed by B-Labs
See [http://genode.org/community/wiki/GenodeOnCodezero]
:'mb':
Support for running Genode natively on the MicroBlaze softcore CPU.
See [http://genode.org/community/wiki/GenodeOnMicroBlaze]
:'host':
Pseudo platform documenting the interface between the generic and
platform-specific parts of the base framework. This is not a functional
base platform.
:'tool':
Source-code management tools and scripts. Please refer to the README file
contained in the directory.
:'hello_tutorial':
Tutorial for creating a simple client-server scenario with Genode. This
repository includes documentation and the complete source code.
:'libports':
This source-code repository contains ports of popular open-source libraries
to Genode, most importantly the C library. The repository contains no
upstream source code but means to download the code and adapt it to Genode.
For instructions about how to use this mechanism, please consult the README
file at the top level of the repository.
:'linux_drivers':
This source-code repository contains the device driver environment for
executing Linux device drivers natively on Genode.
:'dde_ipxe':
This source-code repository contains the device driver environment for
executing drivers of the iPXE project.
:'qt4':
This source-code repository contains the Genode version of Qt4 framework.
Please find more information about using Qt4 with Genode in the repository's
'README' file.
:'ports':
This source-code repository hosts ports of 3rd-party applications to
Genode. The repository does not contain upstream source code but provides
a mechanism for downloading the official source distributions and adapt
them to the Genode environment. The used mechanism is roughly the same
as used for the 'libports' repository. Please consult 'libports/README'
for further information.
:'ports-<platform>':
These platform-specific source-code repositories contain software that
capitalizes special features of the respective kernel platform. I.e.,
for the OKL4 base platform, a port of OKLinux is provided in 'ports-okl4'.
For the Fiasco.OC platform, 'ports-foc' hosts a port of the L4Linux
kernel. For further information, please refer to the README file at the
top level of the respective repository.
:'gems':
This source-code repository contains Genode applications that use
both native Genode interfaces as well as features of other high-level
repositories, in particular shared libraries provided by 'libports'.
Contact
#######
The best way to get in touch with Genode developers and users is the project's
mailing list. Please feel welcome to join in!
:Genode Mailing Lists:
[http://genode.org/community/mailing-lists]